By Roger Wylie
Machine-readable Travel Documents (MRTD) such as passports might at first appear to be a well-defined and relatively straightforward application of NFC for data acquisition, but in fact the application provides a good illustration of some of the complexities of integrating NFC.
The basic parameters for so-called biometric passports are set by the International Civil Aviation Organization, ICAO, in what is known as Document 9303. As with any product nominally produced to a standard, variability can require flexibility in the hardware and software. Each passport or ID card has two or three lines of printed characters intended to be machine-read. Initially this was carried out with an OCR swipe reader, giving rise to a product line that integrates reader and keyboard in a single unit.
Today, products for MRTD-readers read the OCR zone by imaging the entire document and isolating the MRZ (machine-readable zone) in the image. The MRZ provides a key to enable an NFC transaction with the MRTD's embedded integrated circuit, transferring the stored data elements, including the holder's image. The image is then compared to the physical image on the passport page and also, manually or by image processing, with the person presenting the document.
The NFC portion of the e-passport reader includes the hardware and the firmware to seamlessly interface electronic passports and most NFC media types to the host system. The design of the NFC reader employs a dual antenna layout to detect the e-passport chip in a passport when it is laid on the reader as an open book. Having two antennas close to each other at the same resonant frequency poses a new technical challenge – inter-antenna coupling. The antenna circuit incorporates specific circuitry to get around this.
It is worth noting that the reader is, by design, an RF-emitting device. For the power levels and the band in which it operates, it may be license-free in some territories but require licensing and approval in others. It must still pass EMC (electro-magnetic compatibility) testing; demonstrating that in RF-interference terms it is as quiet as possible, while still generating its correct NFC-energizing field. All complete items of equipment must pass such EMC testing, but experience shows that incorporating a module or sub-system that has already gained approval greatly speeds the process.
The MRTD provides an example of an open system where equipment must be able to read all compliant objects that come its way, including some that may be nominally-compliant but poorly-implemented. It also is possible to use the contactless data-transfer capabilities of NFC in a closed system, where reading and exchange of data with tags or devices is intentionally limited to a restricted set of devices.
Also in the travel sector, a recent example is a system that Access IS implemented for an international airline which has issued its loyalty/frequent-flyer account holders with an NFC-readable card. With this document they can check in, verify travel document details and gain access to lounge facilities, all with a touch data exchange. Naturally, with such personal details in the stored data, security is again a prime consideration, no less so than with multi-function payment systems, travel documents or secure-area access systems. This is why industry-standard techniques such as triple-DES encryption of data are employed.
As is the case in many design spaces, transparency and ease of integration comes with sophistication and long, detailed refinement of software code and physical features. Some of the constraints can be quite mundane. For example, the only certain way to verify that an NFC system will correctly interact with every tag or portable device it will ever encounter is to present it with a broad range of examples of each device. Only by working in the field for an extended period is it possible to accumulate a library of real-world test cases and product samples.
Although standard-product NFC ICs often come with reference designs and example code, those off-the-shelf solutions cannot embody the experience that comes with embedding the NFC function into a wide variety of products.
Likewise, off-the-shelf pre-programmed ICs (masked-ROM devices) are available from several sources and may appear to offer a rapid route to incorporating NFC functionality from the ground-up. However, masked code is by definition fixed and can't be fine-tuned. It may not provide compatibility with all of the tag and device types in circulation and it cannot provide the flexibility to optimize the RF field and the communication parameters for reliable communication with a wide variety of tags and devices.
The fastest route to market for NFC system manufacturers will inevitably be to buy in pre-qualified NFC sub-systems that embody the NFC function alone, or provide it ready-integrated with other data-capture functionality.
As phone-hosted NFC chips and contactless payment cards come into more widespread use, there will be a rapidly-increasing opportunity for compatible products to exploit the market opportunity. From self-service kiosks to vending machines, the market will provide an expanding range of goods and services with a touch-payment transaction.
Roger Wylie is a director at Access IS, a company specializing in the design and manufacture of check-in systems, boarding gate readers and mobile phone barcode and NFC readers.